New Zealand Rugby - while sympathetic and moved by the plight of former players battling dementia - says its obligation is to protect the current generation.
Chief executive Steve Tew yesterday said the issue of concussion and potential related long-term health consequences remains complicated with no definitive answers.
"What I would say is that under World Rugby's leadership and with unions taking this matter very seriously there have been some significant developments about how we deal with concussion," he said.
"At Rugby World Cup - the head injury assessment tool and the video analysis being available to the medical staff on the sideline - there were no reported concussions presentations from players who were not removed from the field. Across 48 matches that is a significant step forward."
Tew's comments come after a Herald investigation revealed five men from Taranaki's 1964 Ranfurly Shield-winning team have been diagnosed with dementia, which their families attribute to concussions from their playing days.
Asked how much responsibility New Zealand Rugby should take for these historic cases, Tew said: "It is an incredibly sensitive topic, isn't it? I think we all read the articles of late with considerable compassion and concern.
"But it is a complicated issue and even the highly skilled and trained medical professionals cannot give you a definitive answer on a whole load of really important questions. Right now our responsibility is the current game and making sure we do the right thing for the players who are playing now ... While we will never say enough is enough, I am really comfortable that we are working really, really hard in that regard."
The campaign for change has been a top priority for World Rugby and New Zealand Rugby since 2012. The World Cup signified how much better the game has become at recognising or suspecting concussion and then removing players.
Results from the tournament showed that no player who wasn't removed from the field presented with concussion after they had played. That effectively means the system detected all those who had suffered a serious head knock and successfully prevented everyone with concussion from playing on.
There were other cases where players didn't fail the test but were taken off anyway.
The current concussion testing and protocols have only been in play for the past few years - and there could be several generations of players who suffer health complications that may have some link to head knocks they suffered while playing rugby.
There has also been a sharp rise in ACC claims involving rugby concussions, from $1.1 million in 2010 to $1.9 million last year.
There has yet to be a claim for chronic conditions due to rugby but a spokeswoman said: "It's quite likely that with the growing suite of international medical literature and greater understanding of causation, that we will in the future."
In the United States, the NFL's top health and safety officer acknowledged a link between football-related head trauma and chronic traumatic encephalopathy (CTE) - the first time a senior league official has conceded a connection to the devastating brain disease and other forms of dementia.